Mesoplodon perrini was only described a few years ago, based on five animals stranded on the coast of California (between 33°55'N, 117°15'W and 36°37'N, 121°55'W) from May 1975 to September 1997 (Dalebout et al. 2002). Four of these animals were initially identified as Hector's Beaked Whales (M. hectori), based on cranial morphology (Mead 1981, Mead and Baker 1987, Mead 1989). A fifth specimen was initially identified as a neonate Cuvier's Beaked Whale (Ziphius cavirostris), based on external features. Sightings of two small beaked whales off California in the 1970s which were tentatively identified as M. hectori (Mead 1981) are also likely to be M. perrini (Dalebout et al. 2002). Although similar morphologically, the genetic data do not support a close evolutionary relationship between M. perrini and M. hectori. Instead, these data suggest a possible sister-species relationship with the pygmy beaked whale M. peruvianus (Dalebout et al. 2002, Dalebout et al. 2004).

Justification:
There is no information on global abundance or trends in abundance for this species. It is likely uncommon and potentially vulnerable to low-level threats and a 30% global reduction over three generations cannot be ruled out (criterion A).

All five specimens so far examined have been from southern and central California (between 32° and 37°N), and it is likely that this species is endemic to the North Pacific Ocean (possibly even the eastern North Pacific) (Dalebout et al. 2002).

Like other members of the genus, these species presumably prefers oceanic habitats with waters greater than 1,000 m deep, and the sightings thought to be of this species have occurred in deep waters.

Based on a limited sample of stomach contents, Perrin's beaked whale probably feeds mainly on squids (including Octopoteuthis sp.). The remains of an unidentified invertebrate have been found in the stomach of an animal stranded in California.

All confirmed records have been of strandings (plus two possible sightings), so nothing is known of potential threats. Beaked whales of this genus have been taken occasionally by whalers but are not presently the main targets of any hunt. Entanglement in fishing gear, especially gillnets in deep water (e.g., for billfish and tuna), is probably the most significant threat.

This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).

As a species with an apparently restricted distribution, Perrin’s beaked whale may be vulnerable to the effects of climate change as ocean warming may result in a shift or contraction of the species range as it tracks the occurrence of its preferred water temperatures (Learmonth et al. 2006). The effect of such changes in range size or position on this species is unknown.

Evidence from stranded individuals of several similar species indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.